DisplayPort (DP) architecture utilizes a link service within a source device to discover, configure and maintain a link with devices it connects to. The link service configures the link through what is known as link training. Link training is a process where the correct number of lanes are enabled and the signals are tuned at the required link rate via a handshake between the DisplayPort transmitter (graphics output) and receiver (repeater, hub or display) over an auxiliary channel.
The traditional DisplayPort interface provides an AC-coupled voltage-differential interface. The interface consists of three different channels: a main link, an AUX channel, and a hot plug detect (HPD). The main link features one, two or four scalable data pairs (or lanes) that can be operated at different rates (Gbit/sec). The main link lanes and the AUX channel are differential signals formed from twisted pairs of lines and the HPD is a single wire. The AUX channel is physically like the main link channels, yet is not called upon to transmit data at high speed. The AUX channel and HPD channel are also not required to provide constant data streams. Accordingly, the potential of the AUX channel is thus under-utilized.
The only communication upstream (from receiver to transmitter) is over the AUX channel and HPD channel. The AUX channel, which also provides downstream path alternately with the upstream path, only provides slow transmission (relative to the speed of the main link) and the HPD signal only provides a binary status function. Furthermore, the AUX pair is primarily dedicated to transmitting information regarding the connection quality and existence. DisplayPort does not provide transmission of high speed data other than video display and audio on the main DP channels. Standards have been proposed that send touch screen data upstream along the bi-directional, relatively low speed, AUX channel.
Furthermore, displays are not provided in a manner in which to communicate upstream at high speed to convey the inputs received thereby without additional data connections and wires. Similarly, current DisplayPort technology fails to allow devices such as video cameras, hard drives and network connections to be operated thereover.
Accordingly, high speed upstream data requires additional cabling. Such additional cabling, connectors and ports therefor provide increased costs. In devices such as laptops with hinged screens, additional wires provide additional failure points.
Technology has been developed under the name “Thunderbolt” that combines PCI Express and DisplayPort into a serial data interface. Thunderbolt thus provides for bi-directional data communication. Thunderbolt requires an active cable (copper cables that use silicon chips in the connectors to boost the performance of the cable). The cable has high speed differential pairs of wires for data flow in each direction along with wiring for management purposes. The active nature of the cable and the hardware controllers to handle the data cause the Thunderbolt solution to be relatively expensive.
Accordingly, there exists a need for a device and method that allows for bi-directional high speed data over passive cables. There further exists a need to provide communication that takes better advantage of the capabilities of wires provided for existing DisplayPort lanes. There further exists a need to provide methods and devices that better handle AUX and HPD data to free up data lanes for other data traffic.